The purpose of this study was to develop a microwave exposure system which would provide a plane-wave type field and a variable frequency capability of 1-10 GHz. The system has been assembled and calibrated. The system generates a 90 percent uniform field over a 10 centimeter diameter circle with a power density capability range of 0-20 mW/cm squared. Small biological specimen can be exposed to variable frequencies in either a continuous wave or modulated wave mode.